School of Materials Science and Engineering, Wuhan Institute of Technology, 206 Guanggu No. 1 Road, Wuhan 430205, China.
J Mater Chem B. 2019 Apr 28;7(16):2619-2625. doi: 10.1039/c9tb00249a. Epub 2019 Mar 20.
Intelligent hydrogels responsive to external stimuli have been widely studied due to their great potentials for applications in artificial muscles, soft robotics, sensors and actuators. However, the weak mechanical properties, narrow response range, and slow response speed of many responsive hydrogels have hindered practical applications. In this paper, tough multi-responsive hydrogels were synthesized by using vinyl-functionalized triblock copolymer micelles as macro-crosslinkers and N-isopropyl acrylamide (NIPAM) and acrylamide (AAm) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) as monomers. The P(NIPAM-co-AAm) hydrogels presented tensile strength of up to 1.6 MPa and compressive strength of up to 127 MPa and were tunable by changing their formulations. Moreover, the lower critical solution temperature (LCST) of the thermosensitive hydrogels was manipulated in a wide range by changing the molar ratio of NIPAM to AAm. Responsive hydrogel bilayers were fabricated through a two-step synthesis. A second layer of P(DMAEMA-co-AMPS) was synthesized on the first P(NIPAM-co-AAm) layer to obtain a bilayer hydrogel, which was responsive to temperature, pH and ionic strength changes to undergo fast and reversible shape transformation in a few minutes. This kind of strong and tough multi-responsive hydrogel device has broad prospects in soft actuators.
由于其在人造肌肉、软机器人、传感器和执行器等领域的应用潜力巨大，对外界刺激响应的智能水凝胶受到了广泛的研究。然而，许多响应性水凝胶的机械性能较弱、响应范围较窄、响应速度较慢，限制了其实际应用。本文采用乙烯基功能化的嵌段共聚物胶束作为大交联剂，以 N-异丙基丙烯酰胺（NIPAM）和丙烯酰胺（AAm）或 2-（二甲氨基）乙基甲基丙烯酸酯（DMAEMA）和 2-丙烯酰胺基-2-甲基-1-丙烷磺酸（AMPS）为单体，合成了坚韧的多重响应水凝胶。P（NIPAM-co-AAm）水凝胶的拉伸强度高达 1.6 MPa，压缩强度高达 127 MPa，通过改变其配方可以进行调节。此外，通过改变 NIPAM 与 AAm 的摩尔比，可以在很宽的范围内调节温敏水凝胶的低临界溶解温度（LCST）。通过两步合成制备了响应性水凝胶双层。在第一层 P（NIPAM-co-AAm）层上合成第二层 P（DMAEMA-co-AMPS），得到双层水凝胶，该水凝胶对温度、pH 值和离子强度的变化敏感，可以在几分钟内快速可逆地发生形状转变。这种强韧的多重响应水凝胶器件在软驱动器中有广阔的应用前景。
